Page:Encyclopædia Britannica, Ninth Edition, v. 18.djvu/528

 502 PENNSYLVANIA tion in the quiet Carboniferous sea. There is a striking uniformity in the composition of the whole formation, which is naturally divisible into : (1) upper (Permian) barren-measures ; (2) upper (Pittsburgh) productive Coal-measures ; (3) lower barren-measures ; (4) lower productive Coal-measures; (5) Millstone grit (Pottsville conglomerate) ; (6) Mauch Chunk shale and mountain limestone ; (7) Poeono sandstone and lowest (worthless) coal-beds. These rest on more than 10,000 feet of Devonian rocks. The area of the State actually covered by one or more workable bituminous coal-beds is about 9000 square miles. Dr H. M. Chance s calculation of area, thickness, content, &c. (in a paper read before the Am. Inst. Min. Eng., October 1881), is the most trustworthy yet made. He assumes sixteen important coal-beds, none workable over the whole area of thirty-one counties, only the lowest beds being preserved in ten, and the principal upper beds only in seven of these counties. Beds less than 2 feet thick are ignored. Beds from 2 to 3 feet thick are estimated only from outcrop down to water-level ; beds from 3 to 5, to 150 feet below water-level ; beds over 5, to 400 feet below water-level. Allowing 1650 gross tons per foot to the acre (less 11 per cent, for slate, bone, and sulphur partings, say 1500 gross tons) the mass of beds over 6 feet is 11,000,000,000 tons; of beds between 6 and 3 feet, 19,500,000,000 ; and of beds under 3 feet, 3,000,000,000, making a total of 33,500,000,000 gross tons, 75 per cent, of which can be mined, i.e., 25,000,000,000 tons; of this 10,500,000,000 are in the Pittsburgh bed. An exaggerated statement was current thirty years ago that the Pittsburgh coal-bed within the limits of the State of Pennsylvania would equal the whole annual British coal-trade (then 100,000,000 tons) for 2000 years. According to our present knowledge such an output would exhaust it in a single century. The upper productive Coal-measures, about 300 feet thick, con tain four workable beds, of which the lowest (Pittsburgh) is the mainstay of the coke and iron interests of the seven south-western counties, furnishing to 77 collieries in Allegheny county 4,000,000 tons, to 50 in Fayette county 1,566,000, to 45 in Westmoreland county 2,335,000, to 31 in Washington county 798,000, to 14 in Somerset county 200,000, total nearly 9,000,000 tons mined out of 217 collieries, most of them mere adits into the hillsides, at various levels (from 30 to 300 feet) above the water-level of the Ohio river, or its main branch, the Monongahela river, and its branch the Youghuogheny river. Along these streams railroad stations and slack water pools receive the coal let down by trestle-work slopes from the adits. A few shafts are sunk to the bed where, for short distances, it sinks a few yards beneath water-level. The iron-ores of Pennsylvania formerly sufficed for stocking the furnaces of the State ; but for more than twenty years past large outside supplies have been in demand, the red haematites of Michigan, the magnetic ores of Canada, northern New York, and especially of northern New Jersey, and the limonites of Virginia, not to speak of numerous cargoes of Algerian ore. To understand the native ores it will be necessary to refer to the schedule of the geological formations of the State (see p. 500 above). The more recent formations the Tertiary and the Cretaceous poor in iron ores, are not found in Pennsylvania, being confined to the Atlantic seaboard. The next older formation the Trias also poor in iron ore, makes an independent belt across the State through Bucks, Montgomery, Chester, Lancaster, York, and Adams counties. Hence we have only to consider five sources of supply, (a) the carbonate ores of the Coal-measures, with brown ha-matite outcrops ; (b) the lower Devonian brown haematites ; (c) the Upper Silurian red fossil-ore ; (d) the Lower Silurian brown haematites ; and (e) the Azoic magnetites, some of them apparently in Cambrian rocks, overlaid by Trias, and the rest of them iuterbedded with the oldest (Laurentian ?) gneisses. The ordinary ironstone of the Coal-measures occurs in ball or plate layers throughout the bituminous coal-region, but is almost wanting in the anthracite region. Brown hematite deposits, always connected with the limestone beds in the Coal-measures, were formerly extensively mined, but the supplies of Carboniferous ore of both kinds are far from meeting the present demand, and the make of charcoal iron from them has been virtually abandoned. At the base of the Devonian series the Marcellus still yields con siderable quantities of brown haematite from the outcrop of a fer ruginous clay-bed, but only in two or three noteworthy localities. The Clinton beds of red fossil-ore (soft and rich at the outcrop, hard and lean lower down) at Danville and Bloomsbury, at Frankstown and Hollidaysburg, at Bloody Run and Bedford, kept furnaces going for a good many years, and are still used as mixtures at Johnstown and elsewhere. The Lower Silurian brown haematite mines, however, have been the chief dependence of the industry. They are very numerous in the isolated limestone valleys and along the whole course of the Great Valley. Some of these open quarries are of vast size, and between 100 and 200 feet deep ; furnishing shot and ball and pipe ore of the finest quality, both cold-short and red-short ; and the high reputation of American or Juniata iron is based upon the history first of the charcoal and then of the an thracite make of pig-metal from these special ores. Railroads now carry them long distances to the present centres of the iron manu facture, in the heart of the bituminous coal-region, or in front of the anthracite region, on the Lehigh, Schuylkill, and Susquehanna rivers, where they can be mixed with the subcrystalline iron ores of the South Mountains or of the Highlands of New Jersey. The. South Mountains of Pennsylvania, however, cannot be said to be rich in these last-mentioned deposits, a few of which are indeed mined to a considerable extent ; but no thorough exploration of the range has yet been undertaken to see if the deep-lying strata contain the Canadian and New York magnetites which are to be expected. Some of the oldest and largest mines are situated at the edge of the Trias belt, and were formerly supposed to be of Trias age ; but it seems now probable that they belong to a Cambrian slate forma tion covered by the Trias ; and in all cases they are touched or surrounded by trap-dykes, which cut the Trias or trap-beds that interlie the Trias. The most remarkable of these mines is the &quot; Cornwall &quot; near Lebanon, where great quantities of cupriferous magnetite are obtained by stoping the walls of a vast open quarry. The iron industry of Pennsylvania has always competed with the cotton growth of the southern States and the cotton industry of the eastern States for political power in Congress, to save itself against a foreign importation of rolled iron. The iron-masters of Pennsylvania have led in every debate upon a protective tariff. Pennsylvania has always furnished one-half of the total amount of pig-iron cast in the United States. In 1883 it made 2,638,891 tons out of a total of 5,146,972 tons made in twenty-four States and one Territory. Of these 1,416,468 tons were anthracite pig, 1,184,108 coke and raw coal pig, and only 38,349 were charcoal pig ; and the number of furnaces at the end of 1883 was 142 in blast and 129 out of blast. In like manner Pennsylvania has always rolled more than one-half of the iron and steel rails of American manufac ture, in 1883, for instance, 857,818 tons out of a total of 1,360,694, and of these 819,544 were Bessemer. So of crucible-steel ingots Pennsylvania in 1883 made 63,687 out of a total of 80,455 ; open- hearth steel ingots, 72,333 of a total of 133,679 ; in a word, of all kinds of rolled iron, 1,081,163 tons out of a total of 2,348,874. The petroleum statistics for 1882, partly mixed with those of an adjoining district in New York, show a product of 30,541,740 barrels (of 42 gallons). Vegetation. The vegetation of the State corresponds in variety with the variety of elevation and distance from the seaboard. The mountains are clad with forests of pine, hemlock, oak, beech, maple, walnut, wild cherry, cucumber, dogwood, and laurel, and cultivated apple, cherry, pear, and peach trees grow in the clearings. Wild grapes grow in sheltered places ; wild huckleberries, straw berries, and blackberries flourish. Oats, barley, and timothy grass yield heavy crops. The original forest remains only here and there in secluded spots. All its white-pine timber has been cut, and none grows to replace it. The spruce -pine, hemlock, and oak woods have been girdled by settlers, or barked by tanners and left to die. Extensive iron -furnace tracts have been systematically cut several times ; the deserted charcoal grounds in the anthracite and coke districts have become covered with a dense low growth of oak, maple, birch, dogwood, and other deciduous vegetation. Two other motives have co-operated for the destruction of the original forest, the demand for railway sleepers and the still greater demand for timber and slabs in mines. The annual forest fires, sometimes of enormous magnitude, help to keep the size of forest- wood small, and to cover the uncultivated part of the State with brushwood. The early settlers of the low country also cut with out mercy and without fear ; ifo shadojv was allowed to fall on a field. The traditional practice lasted long ; but the scarcity of wood at length made itself felt. The last generation began to plant ; the present cherishes and multiplies trees, in and around fields, along roads, and on rough ground. The old settled parts of the State are becoming again well wooded. The mountain-ridges will always remain so, for outcrops of sandstone make them rocky, and the terracing of their steep slopes is not yet to be thought of. In the north-western counties the discovery of petroleum in 1859 produced a great demand for derrick lumber, and the ephemeral wooden cities which sprang up during the succeeding twenty-five years caused a rapid bringing under cultivation of at least 5000 square miles, lying between 1000 and 2000 feet above the level of the sea. Two hundred and eighty-four genera and 544 species of plants are enumerated as growing on the plateau of Wayne county, in the north-east corner of the State, a typical portion of the whole upland region, covered with glacial drift -sand and gravel, with innumerable lakes, ponds, and small swamps, lying at various elevations from 1100 to 2000 feet above the sea. Fauna. The zoology of Pennsylvania exhibits that transition stage of its history in which we live. The elk has disappeared ; but the panther (puma) and the small wolf are occasionally met with. The black bear is not by any means extinct, and can always find its way anew into the State from West Virginia. The wild cat is common in the least settled counties. Hedgehogs, ground hogs, weasels, polecats, squirrels of three species, mice of several